Intravascular therapeutic techniques, such as angioplasty procedures, have been developed as alternatives to bypass surgery for treating vascular diseases or other conditions that occlude or reduce the lumen size of portions of a patient's vascular system. During a balloon angioplasty procedure, a balloon catheter is typically inserted intravascularly into a patient through a relatively small puncture, which may be located proximate the groin, and navigated by a treating physician to the occluded vascular site.
A balloon catheter typically includes a balloon or dilating member at the distal end which is placed adjacent the vascular occlusion. Intravascular inflation of the dilating member by sufficient pressures, on the order of 5 to 12 atmospheres or so, causes the balloon to displace the occluding matter. It is known that a number of sequential balloon dilatations may be required to properly revascularize the occluded lumen and restore substantially normal blood flow therethrough. Because the effectiveness of any one balloon dilatation may not be known, it is desirable to view the vascular site after selected balloon dilations to monitor the progress and to determine if any adjustments should be made to the procedure.
One known method for viewing the vascular site is to inject a radiopaque die into the patient's vasculature. X-rays or the like may then be used to view the revascularized portion of the vessel. A disadvantage of this approach is that extended exposure to X-rays can be harmful to both the patient and the treating personnel.
Another more recent approach for viewing occluded sites during an angioplasty procedure is to use an Intra-Vascular Ultra-Sonic (IVUS) device that is attached to the distal end of a guide member, guide wire or the like. The IVUS device can be advanced down the guide wire lumen of a balloon dilatation catheter until the IVUS device is adjacent the dilatation balloon. After a selected balloon dilatation, the IVUS device may provide an image of the revascularized portion of the vessel. A limitation of this approach is that the dilatation balloon often distorts the ultra-sonic image of the vessel, and thus the usefulness of the images provided by the IVUS device are negated.